Process for producing an article of curly interlocking cellulosic fibres and fibrils



y 1961 E. G. H. MAUTHNER EI'AL 2,992,154

PROCESS FOR PRODUCING AN ARTICLE OF CURLY INTERLOCKING CELLULOSIC FIBRES AND FIBRILS Filed April 11, 1957 RAW FIBREs CuTTING TO LENGTH II ENCLOSING 3 WRAPPER BLEACHING 4 A J 1' T w I 11 r 1 j A; r A v DRYING f 4 f r r 5 I 4/ 1, 4, '2 v OPENING +3 MASS OF CURLY FILTER RoD FIBRES AND FIBRILS MILLING IN BINDER MATRIX 7 FIG. 2

SIEVING MASS OF CURLY 8 ENCLOSING FIBRES AND FIBRILS I WRAPPER IN BINDER MATRIX WEB FORMATION AND ADDITIoN OF BINDER FILTER R0D FORMATION CURING 0F BONDING AGENT F l G l INVENTORS.

ERICH G H. MAUTHNER, Deceased, BY STELLA ANNA MAUTHNER, Execum'x.

LAWRENCE L. BAUMANN BY PETER JOHN CLARK ATTORNEYS United States Patent This invention is concerned with improvements in and relating to processes for the production of filter material and to filter material produced by such processes,

According to the present invention there is provided a process for producing a rod of filter material which process consists in subjecting cellulosic fibres 0f the kind produced by decortication from a plant and in which each fibre comprises a bundle of fibrils to a chemical treatment to loosen the bond between the fibrils but without complete disintegration of the fibres into fibrils, subjecting the chemically treated fibres to a mechanical treatment to transform the straight fibres into curled fibres and to disintegrate the fibres partially or completely into fibrils, and thereafter forming. the product into a rod.

Also according to the present invention there is provided a rod of filter material produced by the process specified in the immediately preceding paragraph.

The cellulosic fibres may be subjected to a combing.

and/or beating operation prior to the chemical treatment and/or prior to the mechanical treatment, the combing and/or beating operation being such as to achieve partial longitudinal splitting of the fibres. When the fibres are subjected to such a combing and/or beating operation prior to the chemical treatment this treatment is facilitated.

One or more cutting operations may be employed before the chemical treatment and/or before the mechanical treatment to reduce the fibres to a suitable length. Even when the length of the fibres and/ or fibrils in the resulting rod is not critical one or more such cutting operations may be employed to reduce the fibres to con.- venient lengths for the chemical and/or mechanical treatment.

The rod may have the fibres and/or fibrils thereof bonded together by a bonding agent which may comprise a thermosetting or a thermoplastic material, or a mixture of such materials. At the same time as, or sub.- sequently to, the bonding of the fibres and/or fibrils to one another the exterior of the rod may be bonded to the interior of a tubular wrapper by which the rod is enclosed.

Prior to, or subsequent to, the addition of the bonding agent and before the completion of the bonding operation thereof the material may be compressed to decrease its volume and thereby increase its resistance to the passage of material to be filtered or it may be mechanically expanded to increase its volume and thereby decrease its resistance to the passage of material to be filtered.

The chemical treatment may consist of one or more operations such as bleaching and may include dyeing, and the treatment may be such that the weight of the treated fibres is from 60 to 95% of the weight of the fibres before treatment. The mechanical treatment may consist of disintegration or mechanical expansion in a beater or hammer mill of a known kind, such as the 1 kind in which the fibres are beaten through the apertures in a perforated screen by the action of flails and a stream of The fibres employed preferably are hard fibres such as abaca, henequen or sisal and more preferably are sisal fibres.

Processes in accordance with the present invention for the production of a rod of filter material suitable for use in cigarette filters will now be described, by way of example.

Fibres suitable for use in the processes in accordance with the invention and produced by decortication from the leaves and/or husks and/or stalks of plants are, for example, abaca, coir, flax, hemp, henequen, jute, kenaf, ramie, sisal and sunn.

The chosen cellulosic fibres may first be cut to a length appropriate for the final product and/or convenient. for the operations to be eifected on the fibres, and when the filter rod is intended for the production of cig arette filters a suitable length is 1-6 inches.

The cellulosic fibres may be subjected to a combing and/ or beating operation prior to the chemical treatment, the combing and/or beating operation being such as to achieve partial longitudinal splitting of the fibres. For example, the fibres may be passed to a teasing machine in which they are carried on the periphery of a spiked cylinder of relatively large diameter past one or more smaller spiked cylinders having their teeth intermeshing with those of the larger cylinder, so that the fibres are torn, aligned and longitudinally split by the intermeshing teeth, the fibres thereafter being picked by spiked rollers from the periphery of the large cylinder and discharged from the teasing machine. When the fibres are subjected to such a combing. and/or beating operation prior to the chemical treatment this treatment is facilitated.

The cut fibres are then subjected to a chemical treatment which is carried far enough to reduce the bond between the fibrils of each fibre, but not so far as to result in the disintegration of the fibres into fibrils. Such treatment may, for example, consist of the process known in the textile industry as bleaching. 'In practice an indication that the process has reached the required stage can be obtained by an operator breaking a fibre by hand. If the chemical treatment has not been carried sufliciently far the fibre will still be brittle and will break cleanly without fraying or splitting of fibrils from the fibres, while when the operation has been carried far enough the mechanical action of breaking the fibre causes longitudinal splitting of the fibre, the broken ends appearing frayed. If the chemical treatment is carried too far the fibres will disintegrate completely into fibrils, resulting in a soft, flulfy, tangled mass having the consistency of cotton wool.

An additional action of the chemical treatment is to remove various unwanted, non-cellulosic constituents of the fibres, for example, foreign matter, lignin, pectin, pentosans, fats and waxes. Another indication that the chemical treatment has been carried out to the required extent can be obtained by measuring the loss in weight of the fibres, and in preferred processes in accordance with this invention the weight of the chemically treated fibres is from 60 to of the weight of the fibres before the chemical treatment, the yield obtained varying greatly according to the quality of the raw material.

Another additional action of a chemical treatment that includes a bleaching operation is to whiten the colour, which may often be desirable to improve the appearance of the resulting rod. When such a whitening of the fibres is specifically required then the bleach liquid employed in the chemical treatment includes with advantage an opticalbleach, that is a bleach which will deposit on the fibres a material that is excited to luminescence by light incident thereon, so that the apparent brightness of the fibres is increased; An optical bleach has the added advantage that the fibres bleached thereby appear to have less tendency to becomeyel-low'upon ageing. A suitable optical bleach is for example that sold under the name Tinopal V by the Geigy Company, used in a concentration of approximately 0.01 to 0.05 gram per litre of the bleaching liquid. In other processes a change in the appearance of the fibres, such as whitening or other colouring of the fibres, may be produced by a dyeing operation.

As specific examples may be mentioned chemical treatments found to be suitable for use with the better grades of sisal at present commercially available, such sisal having an average fibre length of approximately 2 to 4 feet and being machine dried prior to the chemical treatment.

(a) Boiling the fibres in a weak solution of caustic soda.

(b) Bleaching the fibres by boiling them in acidified sodium chlorite solution.

The wet fibres from the bleaching operation may be permitted to dry naturally, but it has been found that a more consistent product can be obtained by controlling the drying, for example by carrying it out in a drying machine.

In the accompanying drawing:

FIG. 1 is a self-descriptive flow sheet of the new processes of the invention,

FIG. 2 is a sectional side view of a filter rod in accordance with this invention, and

' FIG. 3 is a sectional end view of the filter rod taken along the line 33 of FIG. 2.

, Each of the chemical treatments referred to above may be adjusted in intensity, for example, by suitable adjustment, of the temperature and/or pressure and/or concentration of the solutions employed.

If the fibres employed were not cut prior to the chemical treatment they may be out prior to the mechanical treatment which follows the chemical treatment. For example, with the sisal fibre referred to specifically above it was preferred to cut it before the chemical treatment to avoid the long fibres clogging the bleaching apparatus. If the chemical treatment apparatus can deal with such long fibres however it may be preferred to defer the cutting until after the chemical treatment.

The purpose of the mechanical treatment is to split the fibres longitudinally and trans-form them from straight fibres into curled fibres, and to disintegrate the fibres partially or completely into fibrils, this treatment thus producing a mass of curly interlocking fibres and/or fibrils, such a mass having great elasticity and being capable of use after bonding as a filter material, e.=g. in a cigarette filter. It is at present believed that the curliness that is imparted to the fibres and fibrils resulting from the disintegration may be due to sudden release of the bonding tensions during the mechanical treatment. In an especially efiective mechanical operation the dried, chemically treated fibres are fed to apparatus in which they are split, curled and shortened by the action of rotating hammers and thereafter, are entrained in a stream of air and forced through the apertures of a perforated screen by fibrous material to dust and in a typical process about cally treated fibres prior to the mechanical treatment to a combing and/or beating operation such as to achieve partial longitudinal splitting of the fibres, the combed and/ or beaten fibres being more readily split by the mechanical treatment. This combing and/or beating op eration may also be effected in a teasing machine in which the fibres are carried on the periphery of a spiked cylinder of relatively large diameter past one or more smaller spiked cylinders having their teeth intermeshing with those of the large cylinder.

The mass of fibres and/or fibrils issuing from the mill can, after further separation if such an operation is provided, be formed into -a rod, for example, by producing a layer of uniform thickness on a conveyor and then gathering the layer by means of a garniture into a rod of uniform cross-section. The rod can be enclosed in a cylindrical wrapper fitting closely about the rod, e.g. of cigarette paper, by wrapping a strip about the rod as it is formed by the garniture to form a cylindrical tube having a longitudinal lapped and stuck seam.

Asa specific example of the effect on sisal fibre of a chemical and mechanical treatment in accordance with this invention may be mentioned the results of microscopic examination of such fibre before and after the treatment. scopic examination showed that an average fibre was composed of about 350 fibrils at the butt end, the number of fibrils decreasing to about 40 at the tip of the fibre. The material resulting from the treatment was of an average length about 1 cm. and was mainly constituted by fibres composed of about 12 fibrils. It will be understood that the figures given are average figures only and individual fibres in a batch may show wide differences from the average figures. The air porosity of the material resulting from' the treatment was meassured by enclosing difierent 1% gram samples of the material in a container of internal volume 4.9 cc. and passing air through the container at a rate of 2 /2 litres per minute. The path length of the air in the material was 6 mm. and the pressure drop between the ends of the path was about 5-7 cms. of water.

For some applications of the filter rod it may be found that the fibres and/0r fibrils thereof do not cohere sufiiciently together and additional coherence may be imparted thereto by the use of various bonding agents. For example, the bonding agent may comprise a solid thermoplastic or thermosettin-g material that is added to the curly, spn'ngy mass in the form of a fine powder, the rod that is subsequently formed being heated to flux the binder and efiect the binding operation. In specific examples of such binding operations 5 to 50% by weight of polythene or other suitable synthetic resin of a particle size less than 50 microns, is added to to 50% respectively by weight of the mass of fibres, the powder being distributed uniformly throughout the mass. Subsequently the rod is heated to above the melting point of the polythene for suflicient time to cause fiuxing thereof. The bonding operation is completed after cooling.

As another example, the bonding agent is in the form of a solution or emulsion, and in specific examples 5 to 50% by weight of polystyrene, or other suitable synthetic resin, are added to 95 to 50% respectively by weight of the mass by spraying or by immersion of the mass therein. The rod which is produced from the mass is heated resistance of the rod to the passage therethrough of the material to be filtered.

In a particular batch of the sisal fibre the micro- If the fibres and/or fibrils of the rod are bonded an external wrapper may not be required to retain the shape of the rod, but such a wrapper may sometimes be supplied to give the rod a desired exterior finish. The rod when formed may be cut into lengths which are supplied direct to a cigarette making machine in which they are incorporated into cigarettes, or instead the lengths may be supplied to a packing station.

We claim:

1. A process for the production of a mass of curly interlocking fibres and fibrils from substantially straight cellulosic fibres of the kind produced by decortication from a plant selected from the group consisting of abaca, coir, flax, hemp, henequen, jute, kenaf, ramie, sisal and sunn and in which each fibre comprises a bundle of fibrils, comprising the steps of subjecting the cellulosic fibres to a leaching operation in an aqueous solution hav ing a solvent effect upon the bonding and gumming materials in the cellulosic fibers to loosen the bond between the fibrils, discontinuing said leaching operation before the fibres have disintegrated into fibrils, drying the leached fibres and thereafter mechanically treating the leached fibres to split the fibres longitudinally at least partly into fibrils and thereby transform the substantially straight fibres into curled fibres each containing a number of fibrils, and forming said curled fibres into a rod.

2. A process in accordance with claim 1 including the step of opening the fibres after the leaching operation to achieve partial longitudinal splitting thereof.

3. A process in accordance with claim 1 including the step of adding a bonding agent to the product before forming it into a rod and thereafter curing the formed rod to bond the material thereof.

4. A process for the production of a mass of curly interlocking fibres and fibrils from substantially straight cellulosic fibres of the kind produced by decortication from a plant selected from the group consisting of abaca, coir, flax, hemp, henequen, jute, kenaf, ramie, sisal and sunn and in which each fibre comprises a bundle of fibrils, comprising the steps of subjecting the cellulosic fibres to a leaching operation in an aqueous solution having a solvent eifective upon the bonding and gumming materials in the cellulosic fibres to loosen the bond between the fibrils, discontinuing said leaching operation before the fibres have disintegrated into fibrils, drying the leached fibres and thereafter mechanically treating the leached fibres to split the fibres longitudinally at least partly into fibrils and thereby transform the substantially straight fibres into curled fibres each containing a number of fibrils and thereafter forming a mass of the product into a predetermined shape.

5. A process in accordance with claim 4 which includes the steps of adding a bonding agent to a mass of the product, before forming the mass into the predetermined shape and thereafter curing the formed product to bond the material thereof.

6. A process for the production of a mass of curly interlocking fibres and fibrils from substantially straight cellulosic fibres of the kind produced by decortication from a plant selected from the group consisting of abaca, coir, flax, hemp, henequen, jute, kenaf, ramie, sisal and sunn and in which each fibre comprises a bundle of fibrils, comprising the steps of leaching the cellulosic fibres by boiling them in an alkaline solution having a solvent effect upon the bonding and gumming materials which serve to bond the fibrils of the cellulosic fibres together to loosen the bond between the fibrils, discontinuing said leaching operation before the fibres have disintegrated into fibrils, drying the leached fibres and thereafter mechanically treating the leached fibres to split the fibres longitudinally at least partly into fibrils and thereby transform the substantially straight fibres into curled fibres, each containing a number of fibrils, and thereafter forming a mass of the product into a predetermined shape.

7. A process as claimed in claim 6 which includes the steps of adding about 5 to 50% by weight of a synthetic resin of particle size less than 50 microns to 95 to 50% by weight of said product before forming the mass into the predetermined shape and thereafter heating the formed mass to flux the resin and bond the material thereof.

8. A process as claimed in claim 6 which includes the steps of adding about 5 to 50% by weight of a synthetic resin in liquid form to 95 to 50% by Weight of said product before forming the mass into the predetermined shape and thereafter heating the resin and product mixture to eliminate the liquid phase and bond the resin-product mixture into the final shape.

9. A process as claimed in claim 6 wherein the said leaching is such that the weight of leached fibres is from to by weight of the fibres before treatment.

10. A process as claimed in claim 6 wherein the fibres are dried prior to said leaching operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,859,847 Rue May 24, 1932 2,765,515 Knudson Oct. 9, 1956 FOREIGN PATENTS 12,149 Australia Apr. 10, 1933 549,551 Great Britain Nov. 30, 1942 

1. A PROCESS FOR THE PRODUCTION OF A MASS OF CURLY INTERLOCKING FIBRES AND FIBRILS FROM SUBSTANTIALLY STRAIGHT CELLULOSIC FIBRES OF THE KIND PRODUCED BY DECORTICATION FROM A PLANT SELECTED FROM THE GROUP CONSISTING OF ABACA, COIR. FLAX, HEMP, HENEQUEN, JUTE, KENAF, RAMIE, SISAL AND SUNN AND IN WHICH EACH FIBRE COMPRISES A BUNDLE OF FIBRILS, COMPRISING THE STEPS OF SUBJECTING THE CELLULOSIC FIBRES TO A LEACHING OPERATION IN AN AQUEOUS SOLUTION HAVING A SOLVENT EFFECT UPON THE BOND.NG AND GIMMING MATERIALS IN THE CELLULOSIC FIBERS TO LOOSEN THE BOND BETWEEN THE FIBRILS, DISCONTINUING SAIDLEACHING OPERATION BEFORE THE FIBRES HAVE DISINTEGRATED INTO FIBRIL, DRYING THE LEACHED FIBRES AND THEREFORE MECHANICALLY TREATING THE LEACHED FIBRES TO SPL.T THE FIBERS LONGITUDINALLY AT LEAST PARTLY INTO FIBRILS AND THEREBY TRANSFORM THE SUBSTANTIALLY STRAIGHT FIBERS INTO CURLED FIBRES EACH CONTAINING A NUMBER OF FIBRILS, AND FORMING SAID CURLED FIBRES INTO A ROD. 